Concentric coil tubing deployment for hydraulic fracture application

ABSTRACT

A method and system for treating a portion of a wellbore. The system includes a coiled tubing string having two fluid flow areas and a valve configured to control the fluid flow out of both flow areas. The system may include at least one isolation element used to isolate a portion of a wellbore. The isolated portion of the wellbore may be treated by pumping fluid down one or both of the flow areas. The valve may be actuated to permit fluid to be pumped down one flow area while fluid is pumped up the other flow area, which may be used to clean out a screen out, treatment, proppant, and/or solids in the wellbore. The coiled tubing string with two fluid flow areas may be used to treat, stimulate, and/or fracture a portion of a wellbore and provide cleanout capabilities, if required.

FIELD OF THE DISCLOSURE

This disclosure relates to coiled-in-coiled tubing. More particularly,this disclosure relates to systems and methods for concentriccoiled-in-coiled tubing for use in treating a wellbore, and the like.

BACKGROUND

Coiled tubing has proven increasingly useful in oil and gas fieldapplications, including workovers, drilling, logging and wellstimulation. Typically, coiled tubing units comprise a continuous lengthof several thousand feet (possibly up to 25,000 feet) of steel tubing,capable of withstanding pressures on the order of 15,000 psi, capable ofbeing repeatedly coiled and uncoiled from a mobile spool, and capable ofbeing injected and withdrawn from oil and gas wells without killing thewell.

Coiled tubing lengths are generally understood in the field to compriseseveral hundred or several thousand feet of continuous, uniform outerdiameter tubing, coilable on a truckable spool and injectable in a boreby means of a coiled tubing injector. The continuous lengths aretypically, although not necessarily, manufactured of steel having alongitudinally welded seam. Resin and fiber polymer materials may alsobe used for continuous tubing. Typically, successive lengths of steeltubing are welded to create a desired unit length. In addition, coiledtubing is expected to be able to withstand significant pressuredifferentials, such as at least 1,000 psi and preferably closer to15,000 psi, and to be sufficiently corrosive resistant and heatresistant to withstand exposure to common hydrocarbons downhole.

The term “truckable spool” means a spool or reel having an outsidediameter of approximately six meters, and typically less, so that thespool can be transported by a boat or by a truck over land and highwaysto a site. Coiled tubing generally has sufficient flexibility to bereeled on a truckable spool and repeatedly coiled and uncoiled from sucha spool or reel. Likewise, coiled tubing's ability to be injected in abore means that the tubing, while flexible, is also sufficiently rigidthat lengths of several hundred or thousand feet can be continuouslythrust, or injected, in bores using coiled tubing injection equipment.

In addition to the applications mentioned above, coiled tubing has alsobeen used in hydraulic fracturing applications. However, one drawback ofcurrent fracture methods is that they implement a single coil of tubingand there may be a risk of getting stuck within a wellbore due to thehigh frequency of screen outs that may occur during some treatmentprocedures, such as fracturing.

Oil and gas operations have known the use of concentric coiled-in-coiledpipe strings. Concentric pipe strings provide two non-well bore channelsfir fluid communication downhole, typically, with one channel, such asthe inner channel, used to pump fluid (liquid or gas or multiphasefluid) downhole while a second channel, such as the annular channelformed between the concentric strings, used to return fluid to thesurface.

Existing systems, however, do not implement concentric or multi-centriccoiled tubing in hydraulic fracturing applications as disclosed herein.

SUMMARY

One advantage of the disclosed system and methods is they provide anefficient system and method for treating a wellbore and recovery processthat enables, if required, the removal of a screen out, treatment,proppant, and/or solids in each fracture created.

One embodiment of the present disclosure is a method of treating awellbore comprising positioning an end of a coiled tubing stringadjacent a portion of a wellbore, the coiled tubing string having afirst flow area, a second flow area, and a valve configured to controlflow out of the first and second flow areas into the portion of thewellbore. The method comprises treating a portion of the wellbore bypumping fluid down at least one of the first and second flow areas.

The method may include pumping fluid down both the first flow area andthe second flow area to treat the portion of the wellbore. The methodmay include isolating the portion of the wellbore prior to treating theportion of the wellbore. Isolating the portion of the wellbore maycomprises setting a plurality of isolating elements. The valve may belocated proximal to the end of the coiled tubing string, The method mayinclude actuating the valve and pumping fluid up the second flow areawhile pumping fluid down the first flow area. The valve may permit fluidand particulates in the portion of the wellbore to flow up the secondflow area. Treating the wellbore may comprise fracturing a formationadjacent the portion of the wellbore. A screen out may have formed in afracture during the fracturing of the formation. The method may includecleaning out the screen out from the portion of the wellbore. Actuatingthe valve and pumping fluid up the second flow path may clean out thescreen out.

One embodiment of the present disclosure is a system to treat a portionof a wellbore. The system comprises a coiled tubing string having afirst flow area and a second flow area and at least one valve configuredto control flow of both the first and second flow areas out of thecoiled tubing string. The system may include at least one isolationelement. The valve of the system may be positioned proximate an end ofthe coiled tubing string. The system may include at least one port thatpermits communication from the first flow area and an exterior of thecoiled tubing string and at least one port that permits communicationfrom the second flow area and the exterior of the coiled tubing string,wherein the at least one valve is configured to control flow out bothports. The at least one isolation element may be actuated to isolate aportion of the wellbore. Fluid may be pumped down the first and secondflow areas from a surface location to treat the isolated portion of thewellbore. The valve may be actuated so that fluid may be pumped downfrom the surface in the first flow area and pumped up to the surface inthe second flow area. A formation of the portion of the wellbore may befractured or stimulated by pumping fluid down both the first and secondflow areas. Fluid pumped up to the surface in the second flow area maybe used to remove a screen out of a fracture of the portion of thewellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a coiled tubing string that may be used totreat a portion of a wellbore.

FIG. 2 shows an embodiment of a coiled tubing string that may be used toclear a screen out during a treatment procedure, such as a hydraulicfracturing.

FIG. 3 shows a cut away view of a coiled tubing string.

FIG. 4 shows a cross-sectional view of an embodiment of a coiled tubingstring.

FIG. 5 shows a cross-sectional view of an embodiment of a coiled tubingstring.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the disclosure is not intended to belimited to the particular forms disclosed. Rather, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 shows a coiled tubing string 100 having a first flow path 101 anda second flow path 102 positioned within a wellbore 1. As describedherein, the coiled tubing string 100 may have various configurationsthat permit two flow paths 101 and 102. The coiled tubing string 100 maybe a coiled-in-coiled tubing string with one flow path down the innercoiled tubing string and the other flow path down the larger coiledtubing string. Alternatively, the coiled tubing string may include aninternal wall that separates the interior of the coiled tubing string100 into two separate flow paths. The coiled tubing string 100 may beused to treat a portion of a wellbore 1. Fluid may be pumped down thefirst flow path 101, as indicated by the arrow in FIG. 1, and out a port111 to treat the wellbore 1. Likewise, fluid may be pumped down thesecond flow path 102, as indicated by the arrow in FIG. 1, and out aport 112 to treat the wellbore 1. A valve 110 may be used to controlfluid flow through the flow paths 101 and 102 in the coiled tubingstring 100. The valve 110 may be positioned adjacent the ports 111 and112 may be used to control the flow of fluid between the ports 111 and112 and the flow paths 101 and 102. Alternatively, the valve 110configured to control the fluid flow through the two flow paths 101 and102 may be positioned at various locations along the coiled tubingstring 100 including at the surface. The configuration of the ports 111and 112 and valve 110 with respect to the end of the tubing string 100and each other is for illustrative purposes only and may be varied aswould be appreciated by one of ordinary skill in the art having thebenefit of this disclosure.

The portion of the wellbore 1 may be isolated from the rest of thewellbore by upper and/or tower isolating elements 120. Various isolationelements 120 that may be connected to a coiled tubing string 100 may beused with the coiled tubing string 100 disclosed herein. For example,the coiled tubing string 100 may be connected to the tool disclosed inU.S. patent application Ser. 14/318,952 entitled “Synchronic DualPacker,” filed on Jun. 30, 2014, which is incorporated by referenceherein in its entirety. The coiled tubing string 100 having two flowpaths 101 and 102 with a valve 110 that may be actuated to control theflow of the flow paths 101 and 102 may be used with or without upper andlower isolation elements 120.

The coiled tubing string 100 may be used during various treatmentprocedures to treat a portion of a wellbore 1. For example, an acid maybe delivered to a production zone to stimulate production. The coiledtubing string 100 having two flow paths 101 and 102 may also be used tofracture a formation 5 of a wellbore 1. As shown in FIG. 1, upper andlower isolation elements 120 may be actuated to isolate a portion of thewellbore 1 that includes a perforation 2 in the wellbore casing. Fluidmay be pumped down either of the flow paths 101 and 102 or may be pumpeddown both of the first and second flow paths 101 and 102 to fracture 6the formation 5. The coiled tubing string 100 may also be used to treatand/or fracture an open hole wellbore as would be appreciated by one ofordinary skill in the art having the benefit of this disclosure.

The portion of the wellbore being treated through the coiled tubingstring 100 may require a clean out procedure. For example, during afracturing procedure a screen out 10 may form in the fracture 6 andwellbore 1 as shown in FIG. 2. Pumping fluid down both the first andsecond flow paths 101 and 102 of the coiled tubing string 100 will notremove the screen out 10 as there is nowhere for the sand forming thescreen out to go. To remove the screen out 10, the valve 110 of thecoiled tubing string 100 may be actuated to permit fluid to be pumpeddown one of the flow paths, such as the first flow path 101, and to bepumped up the other flow path, such as the second flow path 102, asindicated by the arrows in FIG. 2. Fluid pumped up one of the flow paths102 of the coiled tubing string 100 permits the removal of the sandforming the screen out 10 from the isolated portion of the wellbore 1.The coiled tubing string 100 having two flow paths 101 and 102 with atleast one valve 110 that controls the flow paths 101 and 102 to functionas a coiled tubing string 100 to treat a wellbore as well as conduct acleanout procedure. The coiled tubing string 100 may include more thanone valve 110 to control the flow through the flow paths 101 and 102 aswould be appreciated by one of ordinary skill in the art having thebenefit of this disclosure. Likewise, the fluid may be pumped down thesecond flow path 102 and up the first flow path 101 as would beappreciated by one of ordinary skill in the art having the benefit ofthis disclosure.

FIG. 3 shows a cutaway view of an embodiment of a coiled tubing string200 having an inner coiled tubing 201 positioned within an outer coiledtubing 202. The coiled tubing string 200 includes a first flow area 203down the interior of the inner coiled tubing 201 and a second flow area204 between the exterior of the inner coiled tubing 202 and the interiorof the outer coiled tubing 202.

FIG. 4 shows a cross-section view of an embodiment of coiled tubingstring 200 having an inner coiled tubing 201 positioned within an outercoiled tubing 202. The inner coiled tubing 201 may be connected to theouter coiled tubing 202 or may be free to move within the outer coiledtubing 202. FIG. 4 shows the first flow area 203 and the second flowarea 204.

FIG. 5 shows a cross section view of an embodiment of a coiled tubingstring 300 having a first flow area 303 and a second flow area 304. Aninner wall 302 in between the outer wall 301 of the coiled tubing string300 divides the cross-sectional area of the coiled tubing string 300 tofor the two flow areas 303 and 304.

The various configurations of a coiled tubing string 100 having a firstand second flow areas 101 and 102 are for illustrative purposes only.Various configurations may be used to form a coiled tubing string 100having two flow paths 101 and 102 that may be controlled by one or morevalves 110 as would be appreciated by one of ordinary skill in the arthaving the benefit of this disclosure.

Although various embodiments have been shown and described, the presentdisclosure is not so limited and will be understood to include all suchmodifications and variations are would be apparent to one skilled in theart.

What is claimed is:
 1. A method of treating a wellbore comprising:positioning an end of a coiled tubing string adjacent a portion of awellbore, the coiled tubing string having a first flow area, a secondflow area, and a valve configured to control flow out of the first andsecond flow areas into the portion of the wellbore; and treating theportion of the wellbore by pumping fluid down at least one of the firstand second flow areas.
 2. The method of claim 1, wherein treating theportion of the wellbore further comprising pumping fluid down both thefirst flow area and second flow area.
 3. The method of claim 2, furthercomprising isolating the portion of the wellbore prior to treating theportion of the wellbore.
 4. The method of claim 2, wherein isolating theportion of the wellbore further comprises setting a plurality ofisolating elements.
 5. The method of claim 3, wherein the valve isproximal the end of the coiled tubing string.
 6. The method of claim 3,further comprising actuating the valve and pumping fluid up the secondflow area while pumping fluid down the first flow area.
 7. The method ofclaim 3, wherein the valve permits fluid and particulates in the portionof the wellbore to flow up the second flow area.
 8. The method of claim6, wherein treating further comprises fracturing a formation adjacentthe portion of the wellbore.
 9. The method of claim 8, wherein a screenout has formed in a fracture during the fracturing of the formation. 10.The method of claim 9, further comprising cleaning the screen out fromthe portion of the wellbore.
 11. The method of claim 10, whereinactuating the valve and pumping fluid up the second flow path cleans outthe screen out.
 12. A system to treat a portion of a wellborecomprising: a coiled tubing string having a first flow area and a secondflow area; and at least one valve configured to control flow of both thefirst and second flow areas out of the coiled tubing string.
 13. Thesystem of claim 12, further comprising at least one isolation element.14. The system of claim 13, wherein the valve is positioned proximate anend of the coiled tubing string.
 15. The system of claim 14, furthercomprising at least one port that permits communication from the firstflow area and an exterior of the coiled tubing string and at least oneport that permits communication from the second flow area and theexterior of the coiled tubing string, wherein the at least one valve isconfigured to control flow out both ports.
 16. The system of claim 15,wherein the at least one isolation element may be actuated to isolate aportion of a wellbore.
 17. The system of claim 16, wherein fluid may bepumped down the first and second flow areas from a surface location totreat the isolated portion of the wellbore.
 18. The system of claim 17,wherein the valve may be actuated so that fluid may be pumped down fromthe surface in the first flow area and pumped up to the surface in thesecond flow area.
 19. The system of claim 18, wherein a formation of theportion of the wellbore may be fractured or stimulated by pumping fluiddown both the first and second flow areas.
 20. The system of claim 19,wherein fluid pumped up to the surface in the second flow area may beused to remove a screen out of a fracture of the portion of thewellbore.